This proposal seeks to determine the functional activity of polymorphonuclear neutrophils (PMNs) obtained from a single periodontal pocket and/or gingival sulcus. In particular the functional performance of the PMNs as measured by the oxidative burst will be associated with the periodontal health of the sample site and with the types of bacteria found in the subgingival plaque. Also, the functional performance of the PMNs obtained from the peripheral blood of the subject will be compared to that of the PMNs which are recovered from the pocket or crevice. The functional test will be the measurement of ultra-micro quantities of hydrogen peroxide by the oxidation of dichlorfluorescein (DCFH). If functional impairment is found, then we will identify whether this disruption can be associated with clinical disease and with the overgrowth of certain periodontopathic bacteria. These experiments require the application of the flow cytometer to the analysis of the PMNs obtained from a single pocket or crevicular site. These findings could provide the mechanistic link between the overgrowth of periodontopathic bacteria and the underlying tissue pathology. This understanding may lead to more efficient therapy and possibly various interceptive means to prevent periodontal disease from occurring and/or becoming advanced. The elucidation of bacterial effector molecules from the periodontal flora could serve as probes to elucidate PMN physiology and thereby lead to improved diagnostic and therapeutic modalities in medicine. The findings could also provide insights into the pathophysiology of various systemic PMN dysfunctions.